JPH0673027B2 - Silver toner for electrophotography - Google Patents

Description

TECHNICAL FIELD The present invention relates to a silver toner used in electrophotography.

(Prior Art) In electrophotography, a charge image formed on the surface of a photoconductor is developed with a toner having a detecting property and a fixing property, the developed toner image is transferred onto a transfer paper, and then fixed. Then, an image is formed. Various black to color toners are known as electrophotographic toners used for this purpose.
No silver toner is known yet.

(Problems to be Solved by the Invention) On the other hand, in the field where decorativeness is required, electrophotographic copy or printed matter of silver image may be required.
Conventional toners could not be adapted to such applications.

The most common idea for producing a silver toner is to mix a silver metal powder such as a metallic aluminum pigment into the toner, but such a metal powder is very difficult to handle, and it becomes a toner. There is a significant risk of dust explosion when doing so.

Therefore, an object of the present invention is to provide a silver toner applicable to electrophotography.

Another object of the present invention is to provide an electrophotographic toner which is easily manufactured without the above-mentioned danger and which has an excellent silver decorative feeling.

Still another object of the present invention is to provide a silver toner having excellent electrophotographic characteristics.

(Means for Solving Problems) The present inventors have found that when a pigment obtained by coating a thin layer of titanium dioxide on a flaky inorganic crystal substrate is contained in a toner as a colorant, the above-mentioned problems occur. It has been found that a silver toner which has been solved and has excellent electrophotographic properties and decorative effects is provided.

(Function) The colorant used in the present invention is characterized by comprising a flaky pigment in which a thin layer of titanium dioxide is coated on a flaky inorganic crystal substrate. When the toner obtained by dispersing the pigment in the fixing resin medium is fixed on the paper, the scale pressure forms a layered structure in which the scale-like pigments are arranged substantially parallel to the paper surface.

Light incident on a fixed image having such a layered structure is regularly multi-reflected in a multi-layered thin film of titanium dioxide formed on a flaky substrate to enhance metallic luster (pearl luster). At the same time, since the thin film is transparent and uncolored, it exhibits a silver color. That is, the titanium dioxide in the thin film has a large refractive index and thus acts to impart a silver color with metallic luster.

Thus, it will be apparent that the present invention can impart excellent silvery decorative properties to a fixed image of toner.

Not only that, the pigment used in the present invention itself is composed of a chemically stable inorganic oxide, and as a result, troubles such as dust explosion at the time of toner production that occur when using metal powders are not only solved. But not the toner colorant
It has the advantage that it is extremely stable against light rays, heat, corona discharge, ozone, etc., and the image has excellent fastness.

Further, since this pigment is electrically insulative and insensitive to humidity and the like, there is an advantage that the electrophotographic characteristics of the toner are not impaired at all.

(Explanation of Preferred Embodiments of the Invention) Flake Pigment As a flaky inorganic crystal substrate of the pigment, mica (mica) is most excellent in terms of aspect ratio, but any flaky inorganic crystal, for example, Barium sulfate, layered silicate, layered aluminosilicate, etc. can be used. Generally, the aspect ratio (ratio of thickness to length) of the substrate is preferably in the range of about 1:10 to 1:50.

The amount of titanium dioxide deposited on the flaky substrate is determined by the degree of metaclick gloss, but is preferably in the range of 10 to 60% by weight titanium dioxide per pigment, especially 15 to 50% by weight.

The formation of a thin film of titanium dioxide is carried out by a method known per se, for example, by gradually hydrolyzing a solution of a soluble titanium compound in a slurry containing a flaky substrate and gradually depositing titanium dioxide on the flaky substrate. Can be manufactured by.

The scaly pigments used in the present invention are generally 1 to
It is desirable to have an average particle size of 40 μm, especially 5 to 30 μm. That is, if the particle size is smaller than the above range, the metallic luster tends to be lost, while if it is larger than the above range, it becomes difficult to produce a particle size suitable for the toner.

Toner composition As the fixing resin medium, resins used in the production of this kind of toner are used, and as particularly preferable ones,
Various mono- or di-ethylenically unsaturated monomers, particularly (a) vinyl aromatic monomers, (b) acrylic monomers homopolymers and copolymers, etc. are used.

Examples of the monomer (a) include styrene, vinyltoluene, α-methylstyrene, α-chlorostyrene, vinylxylene and vinylnaphthalene.
Examples of the monomer (b) include acrylic acid, methacrylic acid, ethyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, 3-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate. , 3-aminopropyl acrylate, 3-N, N-diethylaminopropyl acrylate, acrylamide and the like.

Other monomers used in combination with these monomers (a) or (b), or alone, include butadiene, isoprene, chloroprene, and other maleic anhydride, fumaric acid, crotonic acid, and itacone. Other examples include ethylenically unsaturated carboxylic acids such as acids or esters thereof, vinyl esters such as vinyl acetate, vinyl pyridine, vinyl pyrrolidone, vinyl ethers, acrylonitrile, vinyl chloride, vinylidene chloride and the like.

The molecular weight of these resins is 3,000 to 300,000, especially 5,000
It is desirable to be in the range of 200,000.

In the toner of the present invention, the above-mentioned silver flake pigment is preferably incorporated in the toner in an amount of 1 to 40% by weight, particularly 5 to 30% by weight. That is, when the amount of the pigment is less than the above range, it is difficult to sufficiently develop a metallic silver color, and when the amount is more than the above range, the fixability is lowered, or economically. Tends to be at a disadvantage.

In the toner of the present invention, the above scale-like pigments can be used alone or in combination with other white pigments or transparent fillers, whereby the color tone and the like can be easily adjusted.

In the toner of the present invention, a toner compounding agent that does not adversely affect the color of the toner and can be regarded as colorless or white or substantially colorless, such as a charge control agent, an offset preventing agent, a pressure fixing property-imparting agent, and a conductive agent, is well known. It may be blended according to the prescription. As the charge control agent, for the purpose of positive charge control, an organic compound having a basic nitrogen atom, for example, a basic dye, aminopyrine, a pyrimidine compound, a polynuclear polyamino compound, aminosilanes or a filler surface-treated with the same is used. Etc. are used, and as the negative charge control agent, a carboxy group-containing compound such as a metal chelate of alkylsalicylic acid is used. These charge control agents are preferably used in an amount of 1 to 10% by weight per toner. Further, in the method of fixing the toner with a hot roll, an offset preventive agent such as silicone oil low molecular weight olefin resins and various waxes can be used in an amount of 2 to 15% by weight based on the whole. In addition, paraffin wax,
Various animal and vegetable waxes, pressure fixing agents such as fatty acid amides and the like may be used in an amount of 5 to 30% by weight based on the whole.

Toner and Production of Toner In the present invention, a toner in which a flake pigment is dispersed in a fixing resin medium is formed into particles having a particle diameter of 5 to 50 μm to obtain a toner.

The toner is manufactured by any means known per se. For example, the above-described coloring agent and charge control agent are blended with a fixing resin medium, if necessary, together with other blending auxiliaries, which are uniformly and uniformly kneaded, and then granulated to obtain a toner.
In molding, it is obtained by cooling the above-mentioned kneaded composition, pulverizing this, and sieving if necessary. Of course, there is no particular problem even if mechanical rapid agitation is performed in order to chamfer the amorphous particles. in this way,
It is important to take care not to destroy the particle structure of the scaly pigment particles themselves during kneading and crushing.

As another method, the fixing resin medium is dissolved in a solvent such as toluene or xylene, and the scaly pigment is dispersed in this,
A toner in the form of spherical particles can be obtained by spray-drying and granulating the resulting stock solution. This method can be said to be an excellent method in that the scale-like pigment is not broken.

Further, the scaly pigment is dispersed in a solvent that dissolves the monomer but does not dissolve the resulting polymer, and the monomer is polymerized in the presence of a radical initiator in this system to obtain a toner. Can be obtained. As the monomer, those exemplified above are preferably used.

(Uses and Effects) According to the present invention, there is provided a gold toner for electrophotography which is excellent in electrophotographic characteristics, decorative effect, durability and the like.

This toner is used not only for ordinary copying on white paper, but also for the purpose of forming a silver image on black paper or colored paper.

(Example) The present invention will be described in the following example.

Example 1. Styrene-acrylic resin (XPA-525 manufactured by Mitsui Toatsu Kagaku Co., Ltd.) 100 parts by weight Low molecular weight polypropylene (Viscole 550P manufactured by Sanyo Kasei Co., Ltd.) 3 parts by weight Pearl pigment (Pearl Glaze MM manufactured by Nippon Koken Kogyo Co., Ltd.) 15 Parts by weight Charge control agent (Bontron E-82, manufactured by Orient Chemical Co., Ltd.) 3 parts by weight After dissolving and dispersing the above mixture in 300 parts by weight of toluene using a homomixer, a spherical powder was obtained by a spray drying method. Then, it was classified into particles of 5 to 50 μm. Further, 0.3% of hydrophobic silica fine particles R-972 (manufactured by Nippon Aerosil Co., Ltd.) was dry-blended with 100 parts by weight of the obtained silver toner.

25 g of the obtained silver toner and ferrite carrier (F141-1
530 Nippon Steel Powder Co., Ltd.) 500g is mixed to make a developer, and DC
When a copy test was performed using a −111C copying machine (manufactured by Mita Kogyo Co., Ltd.), a vivid silver copy was obtained.

When a color paper was used as the transfer paper, a more vivid silver copy was obtained.

Example 2. Polyester resin (Luna peel Arakawa Chemical Co., Ltd.) 100 parts by weight Low molecular weight polyethylene wax (Sun Wax 161-P Sanyo Chemical Co., Ltd.) 2 parts by weight Charge control agent (Bontron E-84 Orient Chemical Co., Ltd.) 2 parts by weight The above mixture was mixed with a ribbon blender, thoroughly kneaded with a Banbury mixer, and then 10 parts by weight of pearl pigment (Pearl Glens MF Nihon Koken Kogyo Co., Ltd.) was added, dispersed in a short period of time, and calendered to give a pearl pigment. Crystals were oriented. Next, finely pulverize with a jet mill fine pulverizer, and collect particles of 5 to 50 µm with a classifier to obtain hydrophobic silica fine particles R-972.
0.3% was dry-blended with 100 parts by weight of the silver toner.

25 g of the obtained silver toner and ferrite carrier (F141-1
530) 500 g was mixed to prepare a developer, and a copy test was conducted with a DC-111C copying machine, and a bright silver copy was obtained. When a color paper was used as the transfer paper, a more vivid silver copy was obtained.

Example 3. Polyacrylic acid (8 g) was dissolved in ethanol (800 ml), and styrene (80 g), methacrylic acid-n-butyl (20 g), pearl pigment (thin plate mica powder coated with titanium dioxide) (5 g) and azobisisobutyronitrile (1 g) were added. Add 1 g of 2-acid phosphoxyethyl methacrylate at the time when the polymerization rate reaches 80% by reacting at 80 ° C. with stirring in a separable flask of 1 under a nitrogen stream at 150 rpm and take 15 hours. To complete the polymerization. The polymer is separated by settling, and ethanol is used for 3
After washing twice, it was dried to obtain 96 g of a silver toner of 5 to 50 μm. Further, 0.1 part by weight of hydrophobic silica fine particles R-972 was dry-blended with 100 parts by weight of the obtained silver toner.

25 g of the silver toner thus obtained and 500 g of a ferrite carrier (F141-1530) were mixed to prepare a developer, and DC-11
When a copy test was conducted using a 1C copying machine, a bright silver copy was obtained. When a color paper was used as the transfer paper, a more vivid silver copy was obtained.

Claims (3)

[Claims] 1. An electrophotographic toner comprising a fixing resin, a colorant and a toner compounding agent, wherein the colorant is a pigment comprising a flaky inorganic crystal substrate coated with a thin layer of titanium dioxide. A silver toner for electrophotography, which is characterized in that 2. A silver toner according to claim 1, wherein titanium dioxide is present in the pigment in an amount of 10 to 60% by weight. 3. A silver toner according to claim 1, wherein the pigment is present in the toner in an amount of 1 to 40% by weight.